JP4712305B2 - Radio wave direction detector - Google Patents

Description

  The present invention relates to a radio wave direction detecting device that detects an arrival direction of radio waves by using an omni antenna and a directional antenna whose amplitude gain function intersects the amplitude gain function of the omni antenna at two points.

  For example, Japanese Patent Application Laid-Open No. 60-147666 “Aerial device for direction finder” is known as this type of radio wave direction finder. The radio wave direction detection device of the above document has a configuration in which four cardioid antennas are provided and their null directions are arranged at intervals of 90 degrees, and these antennas are electrically switched to obtain an output signal from the cardioid characteristics. An amplitude-modulated signal is obtained, and the radio wave direction is detected from this phase.

  In the above radio wave direction detecting device, in principle, four samples are extracted from the cardioid characteristic which is a sine wave system, and the phase of the sine waveform is extracted. There is a problem that the accuracy of the obtained sine waveform is poor. Also, since the sine waveform has a smooth shape and not a sharp shape, the estimated phase tends to have a large error. For this reason, there exists a subject that the precision of the estimated electromagnetic wave direction is bad.

Japanese Unexamined Patent Publication No. 60-147666

  In the conventional radio wave direction detecting device, the antenna of four cardioid characteristics is electrically switched, and the radio wave direction is detected from the phase of the amplitude-modulated signal obtained as a result, so the number of samples for estimation is small, Since the amplitude modulation is smooth, the detected phase is likely to have an error, and as a result, the accuracy of the estimated radio wave direction is poor.

  The present invention has been made in order to solve the above-described problems. The antenna pattern rotating means rotates a directional antenna whose amplitude gain function intersects with the amplitude gain function of the omni antenna at two points. It is an object of the present invention to obtain an accurate radio wave direction detecting device by deriving an evaluation function having a sharp peak in the radio wave incident direction using the difference pattern or power difference between the antenna and the omni antenna.

The radio wave direction detecting apparatus according to the present invention includes an omni antenna, a directional antenna whose amplitude gain function intersects with the amplitude gain function of the omni antenna at two points, and the direction of the antenna pattern characteristic of the directional antenna for each predetermined angle. A first antenna pattern rotating means for rotating, a virtual image suppressing antenna having one null direction, a second antenna pattern rotating means for rotating the direction of the antenna pattern characteristic of the virtual image suppressing antenna at a predetermined angle; The reciprocal of the difference value between the received signal of the directional antenna and the received signal of the omni antenna for each predetermined angle rotated by the first antenna pattern rotating means is obtained, and the reciprocal value for each predetermined angle rotated by the second antenna pattern rotating means is obtained. the inverse of the received signal and the difference value of the virtual image suppression antenna multiplication processing, evaluation function meter for the result and orientation evaluation function And means, a peak detection means for this orientation evaluation function detects a peak having a maximum and a direction finding means for finding a incident direction of the radio wave from the output of the peak detector.

The radio wave direction detecting device according to the present invention includes a cardioid antenna having a cardioid characteristic, an antenna pattern rotating unit for rotating the direction of the cardioid characteristic, an omni antenna, and a rotation angle of the antenna pattern rotating unit. An evaluation function calculation means for outputting an azimuth evaluation function, a peak detection means for detecting a peak at which the azimuth evaluation function is maximized, and a direction detection means for obtaining an incident direction of a radio wave from the output of the peak detection means, The evaluation function calculation means includes a coefficient setting means, a multiplier that multiplies the reception signal of the omni antenna by a coefficient set by the coefficient setting means, and a difference between the reception signal of the cardioid antenna and the output of the multiplier. and calculating subtraction means, a power calculation means for calculating the power of the output signal of said subtracting means, the output of the power calculation means Comprising a reciprocal calculation means for obtaining a number, but that is the configuration in which the orientation evaluation function output of the inverse calculation means for each changing the coefficients to be multiplied by the rotational angle and the multiplier of the antenna pattern rotating means .

  The radio wave direction detecting device of the present invention can rotate the antenna pattern in fine angular increments by the antenna pattern rotating means, calculates a direction evaluation function for each rotation angle, and this direction evaluation function is the incident direction of the radio wave. Since it has a steep peak, it is possible to detect the radio wave direction with high accuracy.

  In addition, the radio wave direction detecting device of the present invention calculates the azimuth evaluation function using a null generated in the difference pattern between the cardioid antenna and the omni antenna multiplied by a coefficient. A sharp peak is shown at a position corresponding to the incident direction, radio wave direction detection can be performed with high accuracy, and direction detection can be performed even when two incident waves are received.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing Embodiment 1 of a radio wave direction detecting apparatus according to the present invention. In FIG. 1, reference numerals 1 and 2 denote cardioid antennas having cardioid characteristics, each having a null. In this direction, the cardioid characteristic of the cardioid antenna 2 is such that the null corresponds to the null of the cardioid antenna 1. 90deg behind. Reference numeral 5 denotes an omni antenna. An omni antenna is an omnidirectional antenna. Reference numeral 9 denotes two antenna pattern rotating means capable of mechanically or electrically rotating the antenna patterns of the cardioid antennas 1 and 2, respectively. Reference numeral 14 denotes a difference between received signals of the cardioid antenna 1 and the omni antenna 5. Subtraction means as difference means, 15 two power calculation means for obtaining the power of each input signal, 6 reciprocal calculation means for obtaining the reciprocal of the output power of the subtraction means 14, and 7 the output of the reciprocal calculation means 6. Multiplication means 10 for multiplying the output of the power calculation means 15 related to the output of the cardioid antenna 2, 10 is a peak detection means for detecting the peak of the inputted evaluation function, and 11 is a direction detection for obtaining the incident direction of the radio wave from the peak. Means. Reference numeral 8 denotes an evaluation function calculation means comprising a subtraction means 14, power estimation means 15, reciprocal calculation means 6 and multiplication means 7. Reference numeral 12 denotes incident wave number estimating means for estimating the incident wave number. The received signals of the cardioid antennas 1 and 2 and the omni antenna 5 are assumed to be x ₁ (t), x ₂ (t), and x ₅ (t), respectively. In the expression of these signals, t is a factor representing time.

When the coordinate axes x and y are defined as shown in FIG. 1 and the angle from the x axis is θ, the amplitude gain functions g ₁ (θ) and g ₂ (θ) with respect to the angle θ of the cardioid antennas 1 and 2 are cardioids. The cardioid antennas 1 and 2 are arranged so as to be defined by the following equation according to the characteristics.

  Further, the amplitude gain function of the omni antenna 5 is as follows.

  Note that the omni antenna 5 is not provided separately. For example, the omni antenna 5 is provided with cardioid antennas having amplitude gain functions as shown in Equation (4) and Equation (5), respectively, as shown in Equation (6) and Equation (7). Since a signal obtained by synthesizing the reception signals of two antennas having symmetrical characteristics of the amplitude gain function is omnidirectional, it may be used. Further, a combination of the received signals of four cardioid antennas may be used as shown in Equation (8).

  These are shown in FIG. From this figure, it can be seen that the cardioid antennas 1 and 2 have nulls in the directions of 270 deg and 180 deg, respectively, and are different by 90 deg. It can also be seen that the amplitude gains of the cardioid antenna 1 and the omni antenna 5 are the same in the 0 deg and 180 deg directions. That is, it can be seen that the difference pattern between the cardioid antenna 1 and the omni antenna 5 has nulls in the 0 deg and 180 deg directions.

  The antenna patterns of these antennas can be rotated by an angle φ in the same direction as the angle θ by the antenna pattern rotating means 9, and the antenna pattern after rotation is represented by the following equation.

This may be mechanically rotated or electrically rotated as shown below. Since Expressions (9) and (10) can be transformed into Expressions (11) and (12), they are generated according to the received signals of the cardioid antennas 1 and 2 and the omni antenna 5 and the angle to be rotated. By using the loads w ₁ and w ₂ shown in Expression (13) and Expression (14), an antenna pattern corresponding to the angle at which the cardioid antennas 1 and 2 are to be rotated can be generated. For example, when the processing of Equation (11) is specifically described, a signal obtained by subtracting the received signal of the omni antenna 5 from the received signal of the cardioid antenna 1 and a received signal of the omni antenna 5 from the received signal of the cardioid antenna 2 are obtained. Two subtracted signals are generated and multiplied by weights w ₂ and w ₁ , respectively. The signal is generated by subtracting the signal after the latter multiplication from the signal after the former multiplication and adding the received signal of the omni antenna 5. The calculation of Expression (12) can be similarly performed by addition / subtraction processing of the received signal and multiplication of the weight. From the above, the antenna pattern of the cardioid antenna can be electrically rotated.

  As described above, in the present embodiment, since the antenna pattern having the cardioid characteristic is rotated, the antenna pattern can be rotated in fine angular increments, and the antenna pattern is more accurate than the conventional technique for switching a plurality of antennas. Can be rotated.

Here, let us consider a case where the time waveform of _one incident wave is s ₁ (t) and this incident wave is incident from the direction θ ₁ . At this time, the received signal of each antenna is as follows.

  The subtracting means 14 subtracts the received signal of the omni antenna 5 shown in Expression (17) from the received signal of the cardioid antenna 1 shown in Expression (15).

It can be seen from the equation (18) that the signal after subtraction becomes 0 in the direction in which the amplitude gain of the cardioid antenna 1 becomes 1. That is, when φ = θ ₁ and φ = θ ₁ + π, the power of the output signal of the subtracting means 14 becomes zero. When the power of the output signal of the subtracting means is obtained by the power calculating means 15 while changing φ, the output value becomes 0 when φ = θ ₁ and φ = θ ₁ + π as described above. In order to find φ where the output value of the power calculation means 15 is 0, the reciprocal calculation means 6 is used to obtain the reciprocal of the power value. FIG. 3 shows the output value of the reciprocal calculation means for φ when the incident wave is θ ₁ = 0 [deg]. As shown in this figure, it can be seen that sharp peaks appear in the incident directions of 0 [deg] and 180 [deg]. However, from this figure, it is impossible to distinguish the peak in the 180 [deg] direction, which is a false image, and the peak in the 0 [deg] direction, which is the true incident direction.

In order to suppress such a false image, the received signal of the cardioid antenna 2 is used. The received signal of the cardioid antenna 2 is given by equation (16), which becomes 0 when φ = θ ₁ + π. That is, since the output value of the power estimation means 15 for obtaining the power of the output signal of the received signal of the cardioid antenna 2 is 0 when φ = θ ₁ + π, the output value of the reciprocal calculation means 6 is multiplied by the multiplication means 7. As a result, the peak of the false image generated at φ = θ ₁ + π can be suppressed. FIG. 4 shows the output value of the multiplication means 7 for φ as an orientation evaluation function. As can be seen from this figure, a sharp peak is obtained at the incident angle of the incident wave. This peak can be detected by the peak detecting means 10 and the direction detecting means 11 can determine the incident direction of the radio wave from the peak position.

As described above, the azimuth evaluation function calculation means 8 shown in FIG. 1 derives the output value of the multiplication means 7 corresponding to the rotation angle φ as the azimuth evaluation function. As expressed by a mathematical formula, when the power value of the output signal of the subtracting means 14 with respect to φ is P _d (φ) and the power of the output signal of the cardioid antenna 2 is P ₂ (φ), the azimuth evaluation function e (φ) is It is given by

Here, the power value P _d (φ) of the output signal of the subtracting means 14 is obtained, but the power P ₁ (φ) of the received signal of the cardioid antenna 1 and the power of the received signal of the omni antenna 5 with respect to φ. P ₅ (φ) may be obtained, and calculated using these, for example, as in Expression (20-1), Expression (20-2), and Expression (20-3).

  This embodiment is effective only when the number of incident waves is one, and when two or more waves arrive, the error in the incident direction estimation result increases. Therefore, as shown in FIG. 12, the incident direction estimation is performed only when the estimation result of the incident wave number estimation means 12 is one incident wave, and the incidence direction is not estimated when two or more waves arrive. The incident wave number can be estimated from, for example, the correlation matrix obtained from the reception signals of a plurality of antennas and the size of the eigenvalue. In addition, a signal separated in the frequency domain may estimate the number of incident waves in the frequency domain by Fourier transform.

  In addition, in the case of a signal that can be separated by a matched filter, such as code multiplex communication, the direction of incidence can be effectively estimated even when multiple waves arrive by performing direction detection after separation.

  The radio wave direction detecting device of the present embodiment can rotate the antenna pattern in fine angular increments by the antenna pattern rotating means, and also uses the null generated in the difference pattern between the cardioid antenna and the omni antenna. Since the azimuth evaluation function is calculated, the azimuth evaluation function shows a sharp peak in the incident direction of the radio wave, and has an effect of being able to detect the radio wave direction with high accuracy.

Embodiment 2. FIG.
FIG. 5 is a block diagram showing the radio wave direction detecting apparatus according to the second embodiment.
In the second embodiment, a cardioid antenna 4 having a null in the direction of θ = 0 degrees is provided, and a subtraction means 14, power calculation means 15, addition means 13, and reciprocal calculation means 6 are provided as a configuration of the azimuth evaluation function calculation means 8. It is the composition provided with. Other components are the same as those in the first embodiment.

In this embodiment, in order to suppress the false image of φ = θ ₁ + π where the output value of the subtracting means 14 for subtracting the received signal of the omni antenna 5 from the received signal of the cardioid antenna 1 is 0, the cardioid antenna 4 received signals are used. The amplitude gain function g ₄ (θ) of the cardioid antenna 4 is given by the equation (21), and the amplitude gain function rotated by the angle φ by the antenna pattern rotating means 9 is given by the equation (22).

From Expression (22), when one incident wave s ₁ (t) is incident from the direction of θ ₁ , the received signal x ₄ (t) of the cardioid antenna 4 is expressed by the following expression.

Power of the received signal x ₄ (t) is next to zero at phi = theta _1, the φ = θ ₁ + π, it can be seen that with a non-zero value. Therefore, it can be seen that when the power of the output signal of the subtracting means 14 and the power of the received signal of the cardioid antenna 4 are added, it is 0 only when φ = θ ₁ . Assuming that the power of the output signal of the subtracting means 14 with respect to the angle φ is P _d (φ) and the power of the received signal of the cardioid antenna 4 is P ₄ (φ), the evaluation function e (φ) is expressed by equation (24). Thus, the peak detecting means 10 can detect the peak having the smallest evaluation function, and the direction detecting means 11 can detect the incident direction of the radio wave from the rotation angle φ corresponding to the peak.

  As in the case of the first embodiment, the reciprocal number calculating means 6 for calculating the reciprocal number of the output of the adding means 13 may be provided, and this peak may be detected. In this case, an orientation evaluation function as shown in Expression (25) is used. As a result, a sharper peak can be obtained in the direction evaluation function, and highly accurate radio wave direction detection can be performed.

Other evaluation functions may be used as long as the principle for suppressing the false image is the same. For example, using the azimuth evaluation function as the power P ₁ (φ) of the received signal of the cardioid antenna 1 and the power P ₅ (φ) of the received signal of the omni antenna 5, the equations (26-1) and (26-2) Similarly, the radio wave direction can be detected with high accuracy even if it is obtained as shown in equations (27-1) and (27-2). In the case of formula (26-1) and formula (26-2), the peak detection means detects the minimum peak, and in the case of formula (27-1) and formula (27-2), the maximum peak is detected. To do.

  This embodiment is also effective only when the number of incident waves is one as in the first embodiment. When two or more waves arrive, the error in the incident direction estimation result increases. Therefore, the incident wave number estimating means 12 may be provided so that the incident direction is estimated only when the incident wave is one wave.

  As described above, the radio wave direction finder according to the present embodiment calculates the azimuth evaluation function using the null generated in the difference pattern between the cardioid antenna and the omni antenna. It shows a sharp peak in the direction, and has the effect of being able to detect the radio wave direction with high accuracy as in the first embodiment.

Embodiment 3 FIG.
FIG. 6 is a block diagram showing a radio wave direction detecting apparatus according to the third embodiment. In FIG. 6, 16 is a coefficient setting means, and 17 is a multiplication means. Description of the components already described is omitted.

In the third embodiment, the received signal of the cardioid antenna 2 can be rotated by an angle φ using the antenna pattern rotating means 9. Here, when the antenna pattern is electrically rotated, as described in the first embodiment, the reception signal of the cardioid antenna 1 and the reception signal of the cardioid antenna 2 are combined by a coefficient corresponding to the rotation angle. To generate. The amplitude gain function g ₂ (θ−φ) after rotating the antenna pattern of the cardioid antenna 2 by φ is indicated by a solid line in FIG. This is expressed by Expression (28), and the received signal x ₂ (t) when the incident waves s ₁ (t) and s ₂ (t) are incident from the incident directions θ ₁ and θ ₂ is expressed by Expression (28). It becomes like 29).

Next, the multiplication unit 7 multiplies the reception signal of the omni antenna 5 by the coefficient k generated by the coefficient setting unit 16. Since the amplitude gain function of the omni antenna 5 is 1, the amplitude gain when it is multiplied by the coefficient k becomes a straight line as shown by the wavy line in FIG. 7 and has two intersections with the amplitude gain function of the cardioid antenna 2. I understand. By changing the coefficient k, the interval between the intersections can be changed. For example, when this interval is set to θ _d , the coefficient k may be set as follows:

The subtracting unit 14 subtracts a signal obtained by multiplying the reception signal of the omni antenna 5 by the coefficient k from the reception signal of the cardioid antenna 2. When two incident waves are received, the output signal x _d (t) of the subtracting means 14 is as shown in Expression (31).

From Equation (31), the power of the output signal x _d (t) is minimized when Equation (32) and Equation (33) are satisfied at the same time. This condition applies to the pattern of the cardioid 2 and the omni antenna. This is the case when the two null directions and the incident directions θ ₁ and θ _{2 of the} two incident waves coincide with each other in the difference pattern of the pattern obtained by multiplying 5 by the coefficient k.

By changing the rotation angle φ and the coefficient k, the interval θ _d between two nulls in the difference pattern is changed, and φ and θ _{d at} which the power of the output signal x _d (t) is minimized are detected. Therefore, the power of the output signal of the subtracting means 14 is obtained by the power calculating means 15, and the reciprocal number is obtained by the reciprocal number calculating means 6 in order to obtain a sharp peak. As a result, an azimuth evaluation function for two variables of the rotation angle φ and the interval θ _d as shown in FIG. 8 is obtained. FIG. 8 shows the case where θ ₁ = 20 [deg] and θ ₂ = 60 [deg]. The peak detector 10 detects a peak having a maximum orientation evaluation function, the direction finding means 11, the rotation angle and azimuth distance theta _d peak is obtained, and outputs the azimuth of the two-wave according to the following equation.

  Since a sharp peak can be obtained as shown in FIG. 8, highly accurate direction detection is possible. Although the reciprocal calculation means 6 is used here, the output from the power calculation means 15 may be used as an azimuth evaluation function, and the peak at which this is minimized may be detected.

  In addition, since this embodiment is suitable for cases where two or less incident waves are received, the incident wave number estimating means 12 is provided in the same manner as in the above-described embodiment, and the incident wave is 1 The incident direction may be estimated only in the case of a wave or two waves.

In the case where the incident wave of one wave to the present embodiment is received, to fix the direction spacing theta _d, in the orientation evaluation function of changing the rotation angle phi, an angle difference that is consistent with the direction spacing theta _d Since two peaks are obtained, it can be distinguished from a case where two waves are incident and only one peak is obtained.

  As described above, the radio wave direction finder according to the present embodiment calculates the azimuth evaluation function using the null generated in the difference pattern between the cardioid antenna and the omni antenna multiplied by the coefficient. The evaluation function shows a sharp peak at a position corresponding to the incident direction of the radio wave, and there is an effect that the radio wave direction can be detected with high accuracy as in the first embodiment. Further, the present embodiment has an effect that direction detection is possible even when two incident waves are received.

Embodiment 4 FIG.
In Embodiments 1 and 2, an example using an antenna having a cardioid characteristic has been shown. However, since a null is used in a difference pattern between a cardioid antenna and an omni antenna, for example, an antenna deviating from the cardioid characteristic is used. 9 and FIG. 10, as long as the antenna has an amplitude gain function having two points of intersection with that of the omni antenna, the antenna can be used as an antenna for forming a difference pattern. In addition, since the antenna used to suppress the false image only uses the characteristic having a null in one direction among the cardioid characteristics, an antenna having one null direction has a cardioid characteristic. It can be used instead.

  Actually, it is difficult to realize an antenna having a complete cardioid characteristic. For example, an antenna having an error Δ whose amplitude gain function is given by Expression (35) is often obtained. However, even in this case, equation (35) becomes 1 at θ = 0 deg and 180 deg regardless of Δ, and can be used in the same manner as an antenna having a cardioid characteristic. For example, FIG. 9 shows the amplitude gain function characteristic when Δ = 0.2, but there is an intersection between the amplitude gain function of the omni antenna indicated by the broken line and the 0 degree direction and the 180 degree direction. It can be seen that it can be used as an antenna for forming a pattern.

  Further, if the cardioid antenna used in the third embodiment is a pattern having one maximum value and one minimum value as an amplitude gain function, the null of the difference pattern from the pattern obtained by multiplying the omni antenna by a coefficient. Exists in two directions, and this direction angle difference can be changed, so that it can be used in place of the cardioid antenna.

  As described above, instead of a cardioid antenna, an antenna having an amplitude gain function offset by Δ from the cardioid characteristic or an antenna having two intersections with the amplitude gain function of an omni antenna can be used instead. In addition to the effects of the first embodiment and the second embodiment, there is an effect that it is easy to realize in manufacturing.

  In the fourth embodiment, an antenna having one maximum value and one minimum value can be used in place of the cardioid antenna. Therefore, in addition to the effect of the third embodiment, the effect of being easily realized in manufacturing. There is.

Embodiment 5. FIG.
In the above description, the case where there is no noise has been described. However, in the case where noise is actually added, for example, as shown in FIG. There is a problem that it becomes difficult and the error increases.

  On the other hand, in the present embodiment, a moving average means (not shown) is provided that inputs an azimuth evaluation function and applies a moving average process to the rotation angle φ direction. For example, the average value of data before and after φ of interest is used as a new orientation evaluation function corresponding to φ. FIG. 12 shows an example in which a moving average process is performed on the orientation evaluation function of FIG. As can be seen from FIG. 12, the azimuth evaluation function becomes a smooth curve by the moving average process, and the position error of the detected peak can be reduced.

  The orientation evaluation function can be smoothed by using, for example, a low-pass filter instead of the moving average processing means.

  Further, the azimuth evaluation function from which the influence of noise is removed can be obtained not by the moving average processing but also by an averaging means for calculating the azimuth evaluation function by calculating the azimuth evaluation function a plurality of times.

  As described above, even when noise is added, the influence of noise can be eliminated by providing a moving average means, a low-pass filter, an averaging means for obtaining the average of the orientation evaluation functions calculated a plurality of times, and the like. There is an effect that a highly accurate radio wave direction detection can be performed.

  It is applied to radio wave direction detection devices used in illegal radio wave monitoring devices, fishing boat collision prevention devices, radio wave buoy detection devices, etc., and detects the incident direction of radio waves with high accuracy.

It is a block diagram which shows Embodiment 1 of the electromagnetic wave direction detection apparatus of this invention. It is an amplitude gain characteristic figure with respect to the electromagnetic wave incident angle of a cardioid antenna and an omni antenna. 6 is a characteristic diagram showing an output value of the reciprocal calculation means in the first embodiment. FIG. 6 is a characteristic diagram illustrating an output value of a multiplication unit according to the first embodiment as a direction evaluation function. 3 is a configuration diagram illustrating a radio wave direction detecting device according to a second embodiment. FIG. FIG. 10 is a configuration diagram illustrating a radio wave direction detecting device according to a third embodiment. FIG. 10 is an output characteristic diagram of multiplication means in the third embodiment. FIG. 11 is an output characteristic diagram of reciprocal calculation means in the third embodiment. FIG. 10 is a characteristic diagram of an antenna that can be used in the fourth embodiment. FIG. 10 is a characteristic diagram of another antenna that can be used in the fourth embodiment. It is the characteristic figure which showed the output value of the multiplication means with respect to rotation angle (phi) when noise was added as an azimuth | direction evaluation function. It is a characteristic view at the time of performing a moving average process with respect to the azimuth | direction evaluation function to which noise was added.

Explanation of symbols

  1, 2, 4: Cardioid antenna, 5: Omni antenna, 6: Reciprocal calculation means, 7, 17: Multiplication means, 8: Evaluation function calculation means, 9: Antenna pattern rotation means, 10: Peak detection means, 11: Direction detecting means, 12: incident wave number estimating means, 13: adding means, 14: subtracting means, 15: power calculating means, 16: coefficient setting means.

Claims (17)

Omni antenna,
A directional antenna whose amplitude gain function intersects with the amplitude gain function of this omni antenna at two points;
First antenna pattern rotating means for rotating the direction of the antenna pattern characteristics of the directional antenna by a predetermined angle;
A virtual image suppression antenna having one null direction;
A second antenna pattern rotating means for rotating the direction of the antenna pattern characteristics of the virtual image suppressing antenna by a predetermined angle;
The reciprocal of the difference value between the received signal of the directional antenna and the received signal of the omni antenna for each predetermined angle rotated by the first antenna pattern rotating means is obtained, and the reciprocal value for each predetermined angle rotated by the second antenna pattern rotating means is obtained. An evaluation function calculation means that multiplies the received signal of the virtual image suppression antenna and the reciprocal of the difference value, and uses the result as an azimuth evaluation function;
A peak detecting means for detecting a peak having the maximum azimuth evaluation function;
A radio wave direction detecting device comprising: direction detecting means for obtaining an incident direction of a radio wave from the output of the peak detecting means. Directional antenna is a cardioid antenna with cardioid characteristics,
The virtual image suppression antenna is a cardioid antenna having a cardioid characteristic whose null direction is delayed by 90 degrees from the directional antenna.
The evaluation function calculation means includes difference means for calculating a difference related to the power or amplitude from the reception signal of the directional antenna and the reception signal of the omni antenna, and power calculation means for obtaining the power of the reception signal of the virtual image suppression antenna. And a reciprocal number calculating means for obtaining a reciprocal number of the output of the difference means, and a multiplying means for obtaining a product of the output of the power calculating means and the output of the reciprocal number calculating means, and the rotation angle of the two antenna pattern rotating means 2. The radio wave direction detecting apparatus according to claim 1, wherein the output of the multiplication means is used as a direction evaluation function for each. Omni antenna,
A cardioid antenna having a cardioid characteristic as a directional antenna whose amplitude gain function intersects with the amplitude gain function of this omni antenna at two points;
First antenna pattern rotating means for rotating the direction of the antenna pattern characteristics of the cardioid antenna by a predetermined angle;
A cardioid antenna as a virtual image suppression antenna having one null direction and having a cardioid characteristic in which the null direction is advanced 90 degrees from the directional antenna;
A second antenna pattern rotating means for rotating the direction of the antenna pattern characteristics of the virtual image suppressing antenna by a predetermined angle;
The difference value regarding the power or the amplitude is calculated from the reception signals of the directional antenna and the omni antenna, and the power of the reception signal of the virtual image suppression antenna is obtained, and the difference value and the reception of the virtual image suppression antenna are obtained. An evaluation function calculation unit that adds the power of the signal, obtains this addition value for each rotation angle of the two antenna pattern rotation units, and sets it as an azimuth evaluation function;
A peak detection means for detecting a value at which the azimuth evaluation function is minimum as a peak;
A radio wave direction detecting device comprising: direction detecting means for obtaining an incident direction of a radio wave from the output of the peak detecting means . The directional antenna is a cardioid antenna having cardioid characteristics,
The virtual image suppression antenna is a cardioid antenna having a cardioid characteristic whose null direction is advanced 90 degrees from the directional antenna,
The evaluation function calculation means includes a difference means for calculating a difference related to the power or amplitude of signals received from the directional antenna and the omni antenna, a power calculation means for calculating power of the reception signal of the virtual image suppression antenna, and An addition means for adding the output of the difference means and the output of the power calculation means, and an inverse calculation means for obtaining the inverse of the output of the addition means, and the inverse calculation for each rotation angle of the two antenna pattern rotation means. 2. The radio wave direction detecting device according to claim 1, wherein the output of the means is used as a direction evaluation function.   Incident wave number estimating means for inputting the received signal of each antenna and estimating the wave number of the incident wave is configured to estimate the incident direction of the radio wave when the incident wave is one wave from the output of the incident wave number estimating means. The radio wave direction detecting device according to any one of claims 1 to 4, wherein A cardioid antenna having cardioid characteristics;
An antenna pattern rotating means for rotating the direction of the cardioid characteristic;
Omni antenna,
Evaluation function calculation means for outputting an azimuth evaluation function for each rotation angle of the antenna pattern rotation means,
Peak detection means for detecting the minimum value of the orientation evaluation function,
Direction detecting means for determining the incident direction of the radio wave from the output of the peak detecting means,
The evaluation function calculation means includes a coefficient setting means, a multiplier that multiplies the reception signal of the omni antenna by a coefficient set by the coefficient setting means, and a difference between the reception signal of the cardioid antenna and the output of the multiplier. A subtracting means for calculating, and a power calculating means for obtaining the power of the output signal of the subtracting means, and the output of the power calculating means each time the rotation angle of the antenna pattern rotating means and the coefficient multiplied by the multiplier are changed. A radio wave direction detecting device, characterized in that the directional evaluation function is used. A cardioid antenna having cardioid characteristics;
An antenna pattern rotating means for rotating the direction of the cardioid characteristic;
Omni antenna,
Evaluation function calculation means for outputting an azimuth evaluation function for each rotation angle of the antenna pattern rotation means,
Peak detecting means for detecting a peak having the maximum orientation evaluation function;
Direction detecting means for determining the incident direction of the radio wave from the output of the peak detecting means,
The evaluation function calculation means includes a coefficient setting means, a multiplier that multiplies the reception signal of the omni antenna by a coefficient set by the coefficient setting means, and a difference between the reception signal of the cardioid antenna and the output of the multiplier. Subtracting means for calculating, power calculating means for calculating the power of the output signal of the subtracting means, and reciprocal calculating means for calculating the reciprocal of the output of the power calculating means, and the rotation angle of the antenna pattern rotating means and the multiplication It is that electric wave direction sensing device characterized in that it is in the configuration and orientation evaluation function output of the inverse calculation means for each changing the coefficients to be multiplied by the vessel.   Incident wave number estimating means for inputting the received signal of each antenna and estimating the wave number of the incident wave is provided, and the direction is estimated when the incident wave is one wave or two waves from the output of the incident wave number estimating means. The radio wave direction detecting device according to claim 6 or 7, characterized by the above. 9. The radio wave direction detecting device according to claim 8, wherein the incident wave number estimating means determines whether the incident wave number is 1 wave or 2 waves from the number of peaks appearing in the output of the peak detecting means. 10. The antenna according to claim 6, further comprising: an antenna having a pattern having a maximum value and a minimum value, the gain being different in accordance with an incident direction of the radio wave, instead of the cardioid antenna. Radio wave direction detection device. 10. The radio wave direction detecting device according to claim 6, further comprising an antenna having a gain characteristic offset from the cardioid characteristic instead of the cardioid antenna.   10. The radio wave direction detecting device according to claim 1, wherein the antenna pattern rotating means electrically rotates the antenna pattern. The antenna pattern rotating means includes two subtracting means for subtracting the received signal of the omni antenna from the received signals of two cardioid antennas each having a cardioid characteristic and having a null direction different by 90 degrees, and the two subtracting means Flip multiply separate coefficients determined according to the angle of rotation to the output signal, and a load means you separately output an output signal of the discrete coefficient multiplied the two subtraction means, two from the load means The radio wave direction detecting device according to claim 12, further comprising a synthesizing unit for synthesizing the outputs of the radio wave.   14. The evaluation function calculating means further comprises a moving average means for inputting the output thereof and performing a moving average process, and the output of the moving average means is used as a bearing evaluation function. The radio wave direction detecting device according to any one of the above.   14. The radio wave direction detecting device according to claim 1, wherein the evaluation function calculating means includes a low pass filter for inputting the output thereof, and the output of the low pass filter is used as a direction evaluation function. apparatus.   The evaluation function calculation means includes a plurality of azimuth evaluation functions calculated at the same angle, and includes an averaging means for inputting the plurality of azimuth evaluation functions and performing an averaging process, and the output of the average means is used as the azimuth evaluation function. The radio wave direction detecting device according to claim 1, wherein the radio wave direction detecting device is a radio wave direction detecting device.   The radio wave direction detecting device according to any one of claims 1 to 16, wherein the omni antenna is configured by two or four antennas having cardioid characteristics arranged symmetrically and their signal combining means. .

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